proxy from environment variable transport tests fail

[xrmx]

Describe the bug:

==================================================================================================== FAILURES =====================================================================================================
______________________________________________________________________________________ test_https_proxy_environment_variable ______________________________________________________________________________________

elasticapm_client = <tests.fixtures.TempStoreClient object at 0x7f7d6cca0810>

    def test_https_proxy_environment_variable(elasticapm_client):
        with mock.patch.dict("os.environ", {"HTTPS_PROXY": "https://example.com"}):
            transport = Transport("http://localhost:9999", client=elasticapm_client)
>           assert isinstance(transport.http, urllib3.poolmanager.ProxyManager)
E           AssertionError: assert False
E            +  where False = isinstance(<urllib3.poolmanager.PoolManager object at 0x7f7d6ccb7c90>, <class 'urllib3.poolmanager.ProxyManager'>)
E            +    where <urllib3.poolmanager.PoolManager object at 0x7f7d6ccb7c90> = <elasticapm.transport.http.Transport object at 0x7f7d6ccb6610>.http
E            +    and   <class 'urllib3.poolmanager.ProxyManager'> = <module 'urllib3.poolmanager' from '/home/rm/work/elastic/apm-agent-python/venv311/lib/python3.11/site-packages/urllib3/poolmanager.py'>.ProxyManager
E            +      where <module 'urllib3.poolmanager' from '/home/rm/work/elastic/apm-agent-python/venv311/lib/python3.11/site-packages/urllib3/poolmanager.py'> = urllib3.poolmanager

tests/transports/test_urllib3.py:126: AssertionError
_______________________________________________________________________________ test_https_proxy_environment_variable_is_preferred ________________________________________________________________________________

elasticapm_client = <tests.fixtures.TempStoreClient object at 0x7f7d6ccade10>

    def test_https_proxy_environment_variable_is_preferred(elasticapm_client):
        with mock.patch.dict("os.environ", {"https_proxy": "https://example.com", "HTTP_PROXY": "http://example.com"}):
            transport = Transport("http://localhost:9999", client=elasticapm_client)
>           assert isinstance(transport.http, urllib3.poolmanager.ProxyManager)
E           AssertionError: assert False
E            +  where False = isinstance(<urllib3.poolmanager.PoolManager object at 0x7f7d6cc86a90>, <class 'urllib3.poolmanager.ProxyManager'>)
E            +    where <urllib3.poolmanager.PoolManager object at 0x7f7d6cc86a90> = <elasticapm.transport.http.Transport object at 0x7f7d6ccacad0>.http
E            +    and   <class 'urllib3.poolmanager.ProxyManager'> = <module 'urllib3.poolmanager' from '/home/rm/work/elastic/apm-agent-python/venv311/lib/python3.11/site-packages/urllib3/poolmanager.py'>.ProxyManager
E            +      where <module 'urllib3.poolmanager' from '/home/rm/work/elastic/apm-agent-python/venv311/lib/python3.11/site-packages/urllib3/poolmanager.py'> = urllib3.poolmanager

tests/transports/test_urllib3.py:132: AssertionError
______________________________________________________________________________________ test_http_proxy_environment_variable _______________________________________________________________________________________

elasticapm_client = <tests.fixtures.TempStoreClient object at 0x7f7d6c35fe10>

    def test_http_proxy_environment_variable(elasticapm_client):
        with mock.patch.dict("os.environ", {"HTTP_PROXY": "http://example.com"}):
            transport = Transport("http://localhost:9999", client=elasticapm_client)
>           assert isinstance(transport.http, urllib3.ProxyManager)
E           AssertionError: assert False
E            +  where False = isinstance(<urllib3.poolmanager.PoolManager object at 0x7f7d6c3422d0>, <class 'urllib3.poolmanager.ProxyManager'>)
E            +    where <urllib3.poolmanager.PoolManager object at 0x7f7d6c3422d0> = <elasticapm.transport.http.Transport object at 0x7f7d6c36e810>.http
E            +    and   <class 'urllib3.poolmanager.ProxyManager'> = urllib3.ProxyManager

tests/transports/test_urllib3.py:120: AssertionError

To Reproduce

1. pip install -r tests/requirements/reqs-base.txt
2. pytest

Environment (please complete the following information)

• OS: [e.g. Linux] Linux
• Python version: 3.11.8
• Framework and version [e.g. Django 2.1]: -
• APM Server version: -
• Agent version: main

Additional context

None

[xrmx]

For some reasons I have localhost in proxy_bypass_environment.